This invention relates to a spread spectrum method and device for spectrum spreading a serial information signal into a spectrum spread signal. This invention relates also to a radio information transmitting method and device for transmitting the serial information signal as a radio information signal by the use of the spread spectrum method and device.
A radio information transmitting device which makes use of a spread spectrum method, is used, for example, in a private branch radio communication network, such as a radio LAN (Local Area Network) and in radio communication by a weak radio wave of a low intensity. Such a spread spectrum method is disclosed in, for example, Japanese Unexamined Patent Publications Nos. 2-299334 (namely, 299334/1990) and 3-238943 (238943/1991). The spread spectrum method is classified into a direct sequence spread spectrum (DS-SS) method, a frequency hopping (FH) method, and a combination of the DS-SS method and the FH method. Among those, the DS-SS method is most often used.
A conventional spread spectrum method which will later be described, is in accordance with the DS method and makes it impossible to transmit a serial information signal as a radio information signal at a high speed. This is because the serial information signal is transmitted as the radio information signal with all bits of the serial information signal subjected to spectrum spreading on the basis of a fixed spreading code which is determined independently of the bits of the information signal.